Metallurgical furnace



Dec. 3, 1946. G. H. s. GRENE 2,412,145

I METALLURQICAL FURNACE I Filed Oct. 6, 1942 2 Sheets-Sheet 1 Inventor ,7 J. Glue/p8 Attorney 1515c. 3, 1946. G H, s, GRENE I 2,412,145

METALLURGICAL FURNACE Filed 001;. 6, 1942 2 Sheets-Sheet 2 F/ez.

Inventor Geo/5J6 #aGi'eize v Attorney Patented Dec. 3, 1946 METALLURGICAL FURNACE George Henry Stanley Grene,-Watford, England, assignor of one-half to Wild-Barfield Electric Furnaces Limited, Watford, England Application October 6, 1942, Serial No. 460,991 In Great Britain October 20, 1941 '7 Claims. 1

Where a powder or small articles have to be treated in special atmospheres as for example in powder metallurgy tube furnaces have been used in a continuous process and small retort type furnaces for a batch method.

In dealing with batches, shallow trays have been supported on a stand on above the other, but the capacity of such a system is limited by the necessity of even heating so far as possible and an even fiow of gas to form the desired atmosphere over the whole of the exposed surfaces.

According to the present invention the material is placed in shallow trays, arranged one above the other in a retort externally heated, or in the case of larger diameter retorts in the space between central and circumferential heating means and gas is supplied in a directed stream over the surfaces of the contents of the trays. The term gas as used herein is intended to refer specifically to gas to form the desired gaseous atmo phere.

In a typical furnace according to the invention a stand or carrier occupies the roughly annular space between central and external structures, both preferably having heating means and carries roughly segmental or tapered trays which can be slid into position so as to form roughly annular layers of trays one above the other. Vertical pipes, which may conveniently be used as the uprights of the stand, afford gas inlets and outlets so positioned as to direct the movement of gas over the surfaces and may be connected to headers or radial branches forming headers at the top (or possibly at the bottom) so that the stand and trays can be loaded into the furnace chamber in a retort and withdrawn through a lid at the top (or possibly at the bottom). Preferably the pipes lie between the trays, and carry supports for the radial edges of the trays, so that heating is obstructed as little as may be.

Other parts of the invention are embodied in a typical form which is illustrated by the accompanying drawings. The parts for which a monopoly is desired are those set out in the claims.

In the drawings- Fig. 1 is a sectional elevation and Fig. 2 a part sectional plan view with the door or lid removed.

Fig. 3 is a broken perspective of the upper portion of the furnace showing particularly the connection of the pipes above the furnace.

The furnace is indicated with an outer wall I, a top door or lid 2 and a central block or chamber 3. Heating means of conventional form are provided, preferably both central and also ex- O1 vapours.

ternal as indicated at 4. Thu as shown the central heater 3 extends vertically from the bottom to nearly the top of the furnace chamber and the external heating resistances 4 extend similarly In the intervening space is cal pipes l and 8 Welded to the top of the retort and welded roughly radial ledges 9 which support the roughly radial edges of superposed lay-' ers of trays 6, any convenient number of traysfor instance six or eight-forming a complete layerv Inlet and outlet branches la, 8a form headers at the top. The gas inlet and outlet pipes l0 and I I can pass out laterally through notches at the top of the furnace wall and can be attached to a gas supply main and outlet duct respectively. At suitable positions to supply each tray are inlet and outlet orifices 1b, 8b (which may be graduated to give an even distribution). The whole stand is suspended by the pipes from the removable top of the retort which is in turn stood in the furnace chamber. Gas distribution can be arranged as convenient; in the illustrated example alternate pipes I of the inner ring of pipes serve to supply the gas over each layer of trays, and the alternate but non-corresponding pipes 8 of the outer ring to collect and remove the gases and water vapour or other resultant gases The remaining pipes 1 and 8, other than those marked with orifices 1b and 8b, do not form gas conduits, but merely for structural supporting parts. And alternatively all the inner or outer pipes or branches may be used with slots or other orifices and baffles if required, the arrangement being such as to direct the gas in an even steady flow as indicated by the arrows over all the surfaces of the material in the trays. It will be understood that as more particularly shown in Figure 1, certain of the pipes 8 are merely structural supports, the remaining pipes 8, such for example as have the orifices 8b in Figure 2, are extended above the top and connected to the outlet pipe I l as shown in Figure 3.

It will be understood that the retort need not necessarily have circular walls and that central as well as external heating is not always essential. Also that the furnace may have uses outside powder metallurgy and that the more detailed description is given by way of an example of a furnace embodying the ideas underlying the invention.

I claim:

1. Apparatus for heat treating powder or small articles including a furnace with external and fices beingso arranged in the said inlet and outlet pipes as to give a directed flow of gas. over the surfaces of material contained in the trays.

2. Apparatus for heat treating powder'or small articles including a furnace withexternal'andj internal structures leaving a roughly. annular space between them, heatingmeans, carriedby.

both the external and the internal structures, an annular retort with a removable lid supportable in the annular space, a frame including tubularmembers, trays supportable in the stand, gas connectionsrfrom outside the furnace to some of the tubularmembers forming inlet pipes, exhaust connections tooutsidethe' furnace to'others; of

the tubular members forming outlet pipes, orifices being-so arranged in the said inlet and outlet pipesas togive a directed flow of gas over the surfaces of material contained inthe trays.

3. Apparatus according to claim 1 wherein the inlet; and outlet pipes pass through and, are secured'to the-lid of ;the retort.

. 4: Applara'tus accordingv to claim 1 wherein the inlet and outlet pipes form uprights of the frame, approximately radial tray supporting members being secured to the uprights.

5. Apparatus according to claim 1 wherein the trays are of tapered form with roughly radial edges.

6.- Apparatus for heat treating powder or small articles in a furnace including a retort, means for heating the retort, a removable lid thereto, a frame fitting in the retort, trays arranged to be supported in the frame in layers each of a number of trays, inlet means arranged to direct treating gasifrom' outside the furnace over the surfaces of the contents of the trays, said inlet means -including tubular members forming part of the structure of the frame, and outlet means arranged toreceive treating gas from the surfaces and deliver it outside the furnace.

'7. Apparatus for heat treating powder or small articles in a furnace including a retort, means for heating the'retorti-a removable lid thereto, a

framefitti-ng; in the retort, trays arranged to-be'.

supportedinthe framein layerseach of a-number of trays, inlet means arranged to direct treating gas from outside the furnace over the surfaces of thecontents of the trays and outlet means arranged to receive treating gas from the surfaces and deliver itoutside the furnace, said outlet means including tubular members forming part ofthe structure'of the frame.

GEORGE HENRY STANLEY GRENE. 

